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Lighting

Clearance Light Mystery

Friday, April 20th, 2012

During the April 2012 Portland, Oregon swap meet, we noticed a very unusual feature on a 1972 Chevrolet ¾ ton. Five GM optional clearance lights were set on the front of the cab above the windshield. The surprise was the inverted dimples stamped at the factory. Amber plastic lenses are secured here. See photo.

Could this mean you received a different cab when you ordered the clearance light option? It seems unlikely these relatively inexpensive plastic lenses would result in the production of a special ordered cab. Could this be? What happens years later when the plastic is sun baked, broken, and GM has discontinued these lenses? Does the truck then run with just the dimples?

We request your help. Can someone explain the story on the 5 raised metal dimples? Email your comments to: jcarter@oldchevytrucks.com.

Amendment to above article:

We appreciate the visitors to our website tech article on the 1971-72 cab clearance lights. Their comments have helped clear the mystery of whether a different cab was required if you ordered the five lights on the top of the cab.

The answer is: “Yes, a different cab roof was made just for these lights”. The answer to the question even goes deeper. The pictured clearance light lenses were offered from 1971 through 1991 and are often referred to as “firemen hats”.

Earlier in 1969-70 the lenses were more rounded and collectors referred to them as “hockey pucks”. It is not yet known if a different cab roof was offered in 1967-68.

We recently found an original 1972 Chevrolet Truck Data Book. Under options they show the 5 roof marker lights as number U01 at a list price of $26.00. It does not go into the requirement of Chevrolet using a different cab. We suspect this was GM’s concern and not the retail buyer.

Our thanks for much of this data goes to Trevor Keiffe in Kansas and Chris Welch in Yukon, Oklahoma.

1972 Chevrolet
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1972 Chevrolet 1972 Chevrolet
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Dim Lights

Thursday, February 11th, 2010

When you notice your head, tail and dash lights are often dim, sometimes even flicker on a rough road, check your cab to frame ground cable

Because the 1967-1972 cab and radiator supports are seperated from the frame by rubber mounts. GM used a small mount woven wire ground strap that by-passes one cab mount. This insures electrical flow even if the cab mount bolts become rusted and electrical current can not flow properly.

You must be under the cab to see this by-pass cable. Yes, GM planned for the trucks later years when rusty mounting hardware caused the lights to dim

dim lights ground strap

1969-1972 Head Light Bezel

Thursday, February 11th, 2010

Contrary to what almost all Chevrolet truck parts dealers list in their catalogs, the 1969-1972 headlight bezels were not alike. Though today all are reproduced in bright-anodized aluminum. This is actually only correct for 1971-1972.

The 1969-1970 bezels were black stamped steel even on the most deluxe models. This color is necessary to blend with the two horizontal black lines in the center grill bar.

If you don’t have the correct stamped steel bezels for your 1969-1970 Chevrolet, paint the 1971-1972 aluminum copies in satin black to match the grill stripes.

1969 headlight bezel 1

1969-1970 on Left | 1971-1972 on Right (above)

1969 headlight bezel 2 1969 headlight bezel 3

1967-1972 Cargo Light

Thursday, February 11th, 2010

The cargo light above the rear window on the 1969-72 GM cab was a factory option and is mostly seen on the more deluxe trucks. This light is controlled from a switch beside the interior dome light and is wired so it will not operate while the truck is in the forward gear. This prevents the bright 21 cp bulb from being on while the truck is on the road which would create road glare to following traffic.

To save GM production costs, the clear rectangular lens in this cargo light housing is the same as a 1969 Camaro right side parking light lens.

Park Light Lens, Amber or Clear

Thursday, February 11th, 2010

When viewing older GM cars and trucks we see both colors of park light lenses. There seems to be no consistency that gives us the proof of what is actually correct, however, it is easy as remembering a year.

Beginning in 1963, federal regulations required park lights to show an amber color. Today, companies reproducing original clear lenses find it easy to run more in the same die using an amber additive. Therefore, in GM trucks most 1954-62 clear lenses now can be found marketed with an equivalent amber style.

One exception is the 1969-1970 Chevrolet truck. Originally it came new with clear lens but behind them are amber park light bulbs giving the required color appearance when illuminated.

4 Speed Back Up Light Switch

Thursday, February 11th, 2010

Four Speed Backup Light Switch – They Did Exist!

4 Speed Back Up Light Switch

The first design of the 4-speed synchronized truck transmission, introduced in 1948, was used through about 1965. About mid series, when the dealer installed backup light increased in popularity, a special switch was attached to the base of the floor shift lever. This was the only location possible as there is no external linkage on a 4-speed.

No doubt regular floor contact with shoes and boots shortened the life of this small electrical switch.

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